Attempts have been made to develop fabrics with heaters by implementing several different approaches in the previous studies. Among them, systems that employ resistor type heaters are very well-known and commercially available. Electrical blankets may be given as an example to this group. However, resistor type heaters result in very high power consumption due to their high resistance. These heaters are very heavy for small and portable applications. Since they run on electricity grid, they threaten the users with the risk of electric shock.
Another type of heated fabric is semi-conductor thin film based fabric heaters. In such heaters, the fabric is entirely coated with a thin film material, which limits breathability of the fabric. Besides, the thin film structure restricts the flexibility of the textile; therefore, its adaptation in wearable technologies is limited.
Finally, carbon nanotube coated fabric heaters were developed. Heating performances of the heatable fabrics developed with carbon nanotubes are very low. Increasing their thermal performances may only be achieved with the use of large amounts of nanotubes. However, in that case both the cost increases and the breathability of the fabric gets negatively affected.
Regarding the known status of the technique, there are similar publications and patent documents to the mentioned invention.
The patent no. US 2011/0285019 A1 is related to the production of transparent and conducting materials by means of metal nanowires. The patent in question identifies that metal nanowires are deposited onto substrates with different methods and the obtained network structure enabled these coatings to be transparent under visible light and electrically conducting. The most common use of silver nanowires is the fabrication of transparent and conducting electrodes. The obtained transparent and conducting thin films are developed as an alternative to the indium tin oxide (ITO) material, which is commonly used in this field. The use of silver nanowire transparent and conducting thin films have been demonstrated in many prototype electronic devices such as organic solar cells, organic light emitting diodes and photodetectors in laboratory.
The publication by Po-Chun Hsu et al. “Personal Thermal Management By Metallic Nanowire-Coated Textile”, Nano Letters (DOI:10.1021/n15036572) is basically related with the back reflection of the infrared beams emitted by the human body through precise control of the silver nanowire density and the fiber spacing of the used fabrics. At the end of the study, it is demonstrated that silver nanowire and carbon nanotube coated fabrics could be heated up under applied voltages. However, the highest temperature obtained is around 50° C. This temperature will be insufficient while in service considering the necessary insulation materials used in the fabrication of the final product.
In the same publication, Po-Chun Hsu et al. also investigated the antibacterial properties of silver nanowire decorated textile against Escherichia coli bacteria. Although the examination of a single type of bacteria is a preferred method in antibacterial tests, it is not sufficient alone in the identification of antibacterial efficacy of the textiles to be used.
U.S. Pat. No. 8,424,119 B2 demonstrates the reflection of infrared light emitted by the human body by means of small circular metallic thin films enabling the conservation of temperature. However, since there is no connection between these thin films, they may not be heated by means of a voltage.
Patent no. WO2011116469 A1 intends to deposit carbon nanotubes onto textile surfaces and thus reflect back the infrared light emitted by the human body. However, the major disadvantage of such studies is the temperature gain, which will be only a few degrees in the case of back reflection.
In patent no. US2010/0118868 A1, carbon nanotube/metal particle mixture is used to heat a vehicle steering wheel by means of “Joule Heating” mechanism. This material showed slow response and low heating performance.
In patent no. WO2005027580 A1, conductive steel fibers were knitted in conjunction with the textile fibers during weaving of the textile. The heater fabricated therein operated with alternating current from the electricity grid. This both restricts the mobile applications and threatens the health of the user.
In Patent no. EP2801655 A1, motives were created on the fabric surfaces by means of carbon nanotubes and carbides of transition metals. Heat generated from the sunlight is transferred to the entire fabric by means of carbon nanotubes. In this method, under sunlight, a temperature increase of only 10° C. can be obtained in twenty minutes.
In patent no. EP2525625 A, heatable textiles were fabricated through the deposition of semiconductor resins onto the textiles. However, the resins entirely covered the textile surface and restricted the breathability of the textile. It also restricted the flexibility of the textile.